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Complications related to Arterial cannulation
Establishing arterial cannulation (usually aortic) is one of the most important events in cardiopulmonary bypass. Commonly used arteries are the Ascending aorta, femoral artery, axillary artery and rarely the iliac arteries ,descending thoracic or abdominal aorta and sometimes the carotid artery in neonatal ECMO. Arterial vascular access can give rise to major complications that can make CPB hazardous. =Ascending aortic cannulation= It is necessary to cannulate the aorta in a nonatheromatous area and with the blood pressure in a normal range. 'Aorta with atheroma' This can cause dislodgement of atheromatous plaques. :*An epicardial echo is more sensitive compared to manual palpation which has actually found to be neither specific or sensitive. :*'Careful minimal handling' is required in such cases or another cannulation site may have to be chosen. :*If an atheromatous plaque is found on incision it may be wiser to close that hole and cannulate elsewere rather than shoving a cannula through an incision in a plaque. :*If there is extensive atheromatous plaques consideration for doing an anaortic OPCAB with arterial grafts with inflow from the IMA's or resection of the aorta or an aortic endartercetomy or a sucker atherectomy of loose atheroma's may have to be planned. 'Hypertensive aorta' *'The blood pressure must be reduced' when trying to cannulate the aorta . Trying to cannulate an aorta which is tense can cause an arterial dissection or tears that can rapidly extend the confines of the purse string. 'Management of such a tear' This may require *'Packing / digital control' while ::*A larger purse string can be placed - if the tear is really limited. With the pressure lowered a side clamp may be placed and precise location of the lumen, and placement of the cannula and repair of any lateral tear may be done. ::* It may be wise to use a pledget if placing additional purse strings. care msut be taken to avoid an "iatrogenic coarctation". ::*An alternate site (for eg femoral artery ) is exposed to allow CPB establishment. *Further planning is based on whether a cross clamp can be placed above the tear and if so it can allow a precise repair/ patching. If not the patient must be prepared for total circulatory arrest to allow precise repair of the torn edges and this may even require patching if the tissues are under tension or even replacement of a part of the ascending aorta or arch depending on the extent of the tear. 'Complications related to the methodology of ascending aortic cannulation' There are diffferent methods of cannulation of the ascending aorta nad each of these can be associated with various complications. Stab cannulation This is a common method of cannulation. Basically a controlled stab inside the aorta is made with either a no 11 or 15 blade and this allows a cannula to be slipped in. A common mistake is to place too small an incision causing a dissection or a controlled tear. Actually if a forceps is used to hold the upper flap and a slightly oblique cut is used , a clean cut can be made into the aorta with virtually no bleeding and precise introduction of the cannula can be done slowly in a unhurried manner. Some surgeons serially dilate the opening with Hegar's or an artery forceps . This has to also be done carefully to prevent an uncontrolled tear. Scratch and cannulate This method requires serially incising the aorta upto the intima'' . This is seen as a bluish streak while incising the media. The tip of the cannula is then ently forced agains t this nad cannulation can be done. This may be problematic if the aorta is floppy and hypotensive like in an aorta in a case which has arrested . Rough manipulation can cause a dissection especially if care has not been tken to incise down to the intima and damage can also occur to the posterior wall if rough "shoving" introduction is done. If the cannula does not go in easily, withdrawal of the cannula, careful inspection is requiredand usually the cause is due to an improper incision failing to rech the intima. Clamp incise and cannulate This requires the application of a purse string either prior or after application of a side clamp. The aorta is opened and this can allow precise application of a purse string through a precise hole. The cannula is placed under vision as the clamp is being released. This method requires quick placement of the purse string if not placed before and cannulation as the side clamp can cause hypotension if it occupies a significant portion of the aorta. This method has to be obviously be avoided in atheromatous aortae. Clamp induced dissection is a distinct possibility by this method. '''Management of a pericannulation dissection Recognition of intraoperative dissection Dissection on cannulation can be recognized by :* '''Bluish swelling of the aorta :* Bleeding from the needle holes :* Increasing line pressure and if perfusion is maintained falling venous reservoir volume Management :*'STOP THE PUMP' :*'CANNULATE AN ALTERNATE SITE' . All open heart patients should have their femoral arteries painted for easy access in case of an intraoperative dissection. A useful alternative is to cannulate the LV apex with a wire reinforced straight cannula (20-22 Fr) in an adult and guide it via the aortic valve and this ensures perfusion of the true lumen in an emergency. :* Rapidly cool to at least 22 degrees The anesthesiologists should prepare for Total circulatory arrest. :* Give Head low position, open the aorta and assess. If there is a distinct tear it can be resected and patched or sutured. GRF glue/Bioglue can be conveniently used. An easy alternative is to invert the aortic adventitia and use it (Floten Flap). And a patch of a Zero porosity graft or Pericardium can be used. If the damage is extensive and not glueable, resection and replacement of the ascending aorta basically involving the whole entry site will be required.. Circulation can be started with deep head low position (Trendlenburg) and slowly fill the aorta to de-air it. Retrograde cerebral perfusion can help in deairing.After this during rewarming the proposed surgical procedure can be done. Cerebral protective measures have to be maintained postoperatively. :*'Avoid cerebal hyperthermia' A relevant links include Massive hemorrhage =Femoral artery cannulation= =Axillary artery cannulation= =Innominate artery cannulation= =Iliac artery cannulation= =Rarer forms of arterial cannulation=